A day after entering Promises, a residential rehab facility in Malibu, Britney Spears has checked out of the treatment center, a source confirms to PEOPLE.

"It was against their advice," says the source. "If she comes back for treatment, Promises will have to assess the situation. Sometimes people come back, but it doesn't look good."

Promises is not a locked-down facility, so a patient is able to leave the program if he or she wants to. Entertainment Tonight and TMZ.com were first to report that Spears had left rehab.

On Tuesday, Spears's manager, Larry Rudolph, told PEOPLE the singer had "voluntarily checked herself into an undisclosed rehab facility today."

Over the weekend, Spears, 25, shaved her head, got two new tattoos and was spotted partying in West Hollywood.

Last week, she visited Eric Clapton's Crossroads Centre in Antigua but left after just one day and headed to Florida, a source told PEOPLE at the time.

Credit: People.com

TMZ has confirmed that Britney Spears has left rehab -- again.

As we first reported, the singer checked into Promises treatment center yesterday. But she just couldn't deal with it and left for home. It's the same story as last week, when Britney was in and out of rehab within 24 hours.

"EXTRA" is reporting that Spears tried to get into a tattoo parlor before going home but it was closed.

Story developing.

Credit: TMZ

Sources tell ET that BRITNEY SPEARS left Promises residential treatment center in Malibu, CA early this morning -- less than 24 hours after checking into the facility.

Following the news that she was in rehab, her manager LARRY RUDOLPH released a statement Tuesday, saying, "Britney Spears has voluntarily checked herself into an undisclosed rehab facility today. We ask that the media respect her privacy as well as those of her family and friends at this time."

It all started over the weekend, when Britney made headlines by taking a pair of electric shears to her head and shaving off all of her hair. The mom of two small children visited a Tarzana, Calif. hair salon on Friday, and asked veteran stylist ESTHER TOGNOZZI to shave her head.

"All of a sudden there were people knocking on my door saying, 'Open the door,' and they said Britney Spears needs to come in," Tognozzi tells ET.

"She sat on my chair and wanted her hair shaved off and I said, 'I'm not doing it,'" she continues. "I said, 'Maybe you're having, you know, a hormonal moment [and] tomorrow will be different, let's talk about it,' and she said, 'No I want my hair shaved off.'" When Tognozzi hesitated, Brit used a pair of electric clippers to shave her hair off herself. "[She] came over and sat in this chair ... and proceeded shaving off her hair."

The songstress was then spotted at a Los Angeles-area tattoo parlor, where she got two new pieces of body art.

This shocking move comes on the heels of People magazine's report that last week the singer checked in and abruptly checked out of ERIC CLAPTON's Crossroads Centre, a rehab facility in Antigua, leaving after just one day and returning to Southern California on Friday.

Ever since separating from Federline in November, Britney has been making headlines for her party-hopping and no-panty-wearing ways.

Besides being caught numerous times by paparazzi flashing her goods while getting in and out of her rides, she has also been spotted everywhere, from Malibu to Las Vegas to New York City, making the rounds at the hottest clubs.

First she was seen out a number of times with PARIS HILTON. Soon that friendship reportedly fizzled, and Britney started spending time with ISAAC COHEN until their reported recent split.

I really hope this isn't true. Word on the street though is that she is moving to a more secluded Treatment facility. Only time will tell.